Scientific Endeavours and Achievements

The Antarctic Ross Sea Lithosphere Study (ARSLS) was planned to visit a number of key volcanic cones in the vicinity of Ross Island and the foothills of the Transantarctic Mountains to collect xenoliths derived from the lower continental crust and lithospheric mantle. Most of the localities visited had been sampled by Gamble on previous occasions, but many of these were helicopter supported visits with little opportunity for detailed sampling. The aim for the 1992/93 season was to establish a field camp and spend several days undertaking exhaustive sampling. At this stage we are pleased to report that our sampling was both rigorous and highly successful as may be judged by the 10001b + of rocks being returned to New Zealand.

The ARSLS team consisted of John Gamble (Event Leader), Richard Wysoczanski (PhD student) and Jonathan Brooker (BSc Hons student).

The party departed for Antarctica on Monday 10th December 1992 after a delay of 1 day due to bad weather in McMurdo. Between the 11th - 13th November Wysoczanski and Brooker attended Field Training (Gamble day only) and assembled field gear. During this exercise, Wysoczanski and Brooker took the opportunity to sample xenoliths from Half-Moon Crater, adjacent to Castle Rock on Hut Point Peninsula. On Saturday 14th November the party travelled north along the length of Hut Point Peninsula and collected xenoliths from Sulphur Cones (166° 45′E, 77° 48′S) and Turtle Rock (166° 47′E, 77° 44.5′S). A wide range of xenoliths was collected from both localities. On 16th November the party moved by helicopter to Black Island, to a locality immediately south of Mt Aurora (163° 23′E,78° 14′S) to visit a cone initially sampled by Gamble in the 1984/85 season. Careful collecting and more thorough exploration of the locality resulted in a complete crust-mantle suite being collected, considerably extending that made on the previous visit. The party returned to Scott Base on 18th November 1992.

The party left Scott Base for Foster Crater (162° 57.00′E, 78° 23.73′S) on the 20th November, arriving at the crater amidst gathering cloud conditions which actually obscured the previous camp site used by Gamble in 1982/83 and 1984/85. As a result we camped on hard snow on the south of the crater, several hundred feet above the Koettlitz Glacier. The party encountered page break extreme winds (>75 - 80 knots) at this locality which eventuated in an early rescue (see logistic report) on 23rd November. However, before the high wind situation had developed, a comprehensive set of xenoliths was recovered. In particular, we added to the number of upper mantle spinel lherzolite samples and the granulite lower crustal suite.

The final destination in our search for xenoliths was Cape Bird and the basalt scoria cone called Cinder Hill (166° 25′E, 77° 16.53′S). On this trip the K-048 party had an extra field assistant in Vivienne Taylor, from the Scott Base staff. The field party departed Scott Base on 27th November, returning 1st December. Fresh granular spinel lherzolite xenoliths were recovered from a new locality to the south of Cinder Hill. These xenoliths were contained in dense black lava, in contrast to most other xenolith occurrences, which are in poorly welded, frequently oxidised, scoria deposits.

In summary, the 1992/93 season proved very successful, a new xenolith locality was located at Cape Bird and previous collections from Turtle Rock, Sulphur Cones, Black Island and Foster Crater were greatly enlarged and expanded. Work on these samples will commence as soon as they are returned from the ice.